mapreduce下的求和（运行成功，必采纳）急急急

Question

问题：求震级＞6的地震总数
要求：map reduce job分开写

以上部分数据代表时刻，震级，经度，纬度，深度，地区。

Answer 1

针对你的地震数据，我写的代码解决方案如下，望采纳：

Map阶段代码：

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class EarthquakeMapper extends Mapper<LongWritable, Text, IntWritable, IntWritable> {

  private static final IntWritable ONE = new IntWritable(1);

  @Override
  public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
    // 解析地震数据
    String[] data = value.toString().split(",");
    float magnitude = Float.parseFloat(data[1]);
    // 如果震级大于6，输出(1,1)
    if (magnitude > 6) {
      context.write(ONE, ONE);
    }
  }
}

Reduce阶段代码：

import java.io.IOException;

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Reducer;

public class EarthquakeReducer extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {

  @Override
  public void reduce(IntWritable key, Iterable<IntWritable> values, Context context)
      throws IOException, InterruptedException {
    // 计数器初始化为0
    int count = 0;
    // 遍历所有(1,1)的二元组，计数器加1
    for (IntWritable value : values) {
      count += value.get();
    }
    // 输出震级大于6的地震的总数
    context.write(key, new IntWritable(count));
  }
}